How flexible is 0.5mm aluminum sheet ?

[TRITON]

I have a tube(A) to fit inside another tube(B), and the difference is 1mm. Tube A is the narrower.
(This is a bicycle thing)

I need the A to be a tight fit into B.

I used to have some alloy sheet years ago, not as thick(maybe 0.3mm) which i used to wrap(bike terminology time) the headset cups with to fit into the headtube on the frame, to take up any differences(sometimes theres gaps or its snug, rather than tight. Headset cups into headtubes are usually fitted using a simple press(threaded rod,couple of big washers,nut on each end. Tighten the nuts draws the two together forcing it into the headtube)

A- is a headset cup measuring 49mm in diameter
B- is a bicycle headtube measuring 50.2mm in diameter

 

[Homeless Squirrel]

I have a tube(A) to fit inside another tube(B), and the difference is 1mm. Tube A is the narrower.
(This is a bicycle thing)

I need the A to be a tight fit into B.

I used to have some alloy sheet years ago, not as thick(maybe 0.3mm) which i used to wrap(bike terminology time) the headset cups with to fit into the headtube on the frame, to take up any differences(sometimes theres gaps or its snug, rather than tight. Headset cups into headtubes are usually fitted using a simple press(threaded rod,couple of big washers,nut on each end. Tighten the nuts draws the two together forcing it into the headtube)

A- is a headset cup measuring 49mm in diameter
B- is a bicycle headtube measuring 50.2mm in diameter

You might find you have come across cross standards issue? As the frame could be Ahead etc types yes the Yanks have a lot of changes for sake of changes! and Ahead frame headstocks are bigger than the old style threaded headsets. 1 inch.1,1/8".1,1/4"
https://www.parktool.com/en-int/blog/repair-help/headset-standards

 

[Fitzroy]

You are describing the use of a shim, my feeling is that 0.5mm aluminium will be stiff enough that it will not bend around a 49mm diameter without permanent deformation. You may be better off with several shims adding up to the desired thickness.

 

[TRITON]

You might find you have come across cross standards issue? As the frame could be Ahead etc types yes the Yanks have a lot of changes for sake of changes! and Ahead frame headstocks are bigger than the old style threaded headsets. 1 inch.1,1/8".1,1/4"
https://www.parktool.com/en-int/blog/repair-help/headset-standards

Its a modern bike. the headset and headtube sizes are for want of a better term a ***** joke.

Bike arrived with a damaged fork. (From CRC, which is now closed down)

Removed fork.
Fork steerer is 1 1/8"
So normally where the crown race sits, it should be for 1 1/8"(actually 30mm standard size crown race.
Not so on this fork. Where the crown race sits it has a wide/thick section bringing the crown race to 1 1/4" size.
Lower bearing headset cup is 1 1/4"
Remove lower bearing cup - measure headtube size for replacement
Measures 1 1/2"

So the headtube is tapered size -
Tapered is normal these days. my sus Emtb is is tapered, my sus mtb is tapered, and ive a number of forks, Fox factory, pike,lyric are tapered, but to long travel for this bike

What is causing the issue is its an 1 1/8" fork, going into a 1 1/2" headtube, thats been reduced to fit a 1 1/4" headset.

1 1/2" is a standard size. But theres more than a single 1 1/2" sizing. We can have 1 1/2" that is 49.7mm(known as a true 1 1/2", but also under the 1 1/2" heading we can have 55.9mm

We have traditional standard, integral, semi-integrated and even in a 1 1/2" lower headtube can all be slightly different sizes. Its all very confusing these days :lol:


SO.
To make it work, i buy a fork with 1 1/8" steerer, the standard 1 1/8" crown race, and to fit to the frame a stepdown lower headtube bearing cup(Hope type 'D') that is 49.7mm outer diameter, for a 1 1/2" headtube that should have fitted without any issue.
Only its loose, and its lose because the manufacturers of this type of bike are complete tw**s and decided to do everything on the cheap.

So, to take up that difference i need to wrap the lower cup where it goes into the frame with something to take up the difference.

I've not got the best of digital calipers, so readings arent as accurate as it goes, but from the known sizes i can guess what they are supposed to be.

I basically need a tape i can initially wrap round, and add more til the fit is as tight as it should be. I've access to a proper headset press, and have fitted a number so know what Im doing on that account.


I admit this was a bit of an impulse buy, £500 for what is a £1500 commuter type ebike, which is something i need as my other emtb is close to £6k, and i want something i can take into the city and leave there while i go shopping and not worry about it as you would if it were a £6k affair.

It's been a bloody headache, not helped by the manufacturer 4r5ing about with the sizes and fittings 5to save money. But it is what it is and im sure i can eventually sort it.

Just need to find a good quality alloy tape what isnt basically tissue paper.

'Ahead', 'threaded' if only it were that simple these days

 

[TRITON]

You are describing the use of a shim, my feeling is that 0.5mm aluminium will be stiff enough that it will not bend around a 49mm diameter without permanent deformation. You may be better off with several shims adding up to the desired thickness.

Yeah, in the past ive used an alloy tape stuff. came in a sheet, self adhesive. But ive long since ran out of that, and as it was a gift from a bike mechanic, getting more of the exact same thing isnt likely.

As above, with tape i can put on a couple of wraps, check fit, and add another wrap or such as needed. Tape needs to be dense, hence needing something metal.
So i thought that knowing my approximate sizes, something like aluminum would b a good choice, but if you think that too stiff, then tape would be a better

Any suggestions on that front ?

 

[Sideways]

Use beer can or takeaway trays ?
Both of those are flexible enough to wrap like you describe.
Takeaway tray is very soft.
Beer can is drawn so relatively hard but thin and will flex around anything as big as an inch diameter.
You could use steel shim stock, bought on the roll, but for a 2" diameter bend it will need to be pretty thin. Maybe less than 0.1mm
You need to make up 0.6mm radius so maybe beer can will do, possibly superglue between the layers as you go to stop it unwinding when you let go.

 

[ChaiLatte]

...my feeling is that 0.5mm aluminium will be stiff enough that it will not bend around a 49mm diameter without permanent deformation.

I think something has gotten lost there between the thoughts in your head and the words on the page.

Any flat sheet, no matter what its thickness, has to suffer permanent deformation in order to form it into a circle.

Maybe you could reword your contribution to clarify the point you are trying to make.

In any case, I am not sure that implying I cannot wrap a strip of 0.5mm aluminium sheet around a scaffold tube has much basis in fact. The challenge is more a practical one - eliminating the flats at the beginning and the end of the bend. In effect, you have to wrap the sheet around more than 360 degrees and then trim the ends to suit.

 

[MorrisWoodman12]

I remember years ago when I was still a teenager I annealed 1/8" aluminium sheet on my mother's gas hob prior to using it to reduce the compression on my first motorcycle. (DOT - Devoid of Trouble! My big fat arras- with a Villiers 9E). Smear the 'top' surface with soap and heat gently until the soap goes dark and allow to cool. 0.5mm sheet should then bend quite easily.
Helpful? I hope so.
Martin

 

[StephenArfer]

I believe the best way of creating what is essentially a thin-wall split bushing, is to roll one using small bending rolls. The technique and tooling is well illustrated here: https://www.nickbaines.me.uk/Bending_rolls.html

Many hobbyist model engineers will have small bending rolls, many to the same GH Thomas design shown in the link above. I would suggest that you join a model engineering forum and post a request for someone to roll a shim for you. I would suggest 0.5mm or 0.020" brass would be a better material for the job. This would be routine for many model engineers along with the annealing technique.

 

[TimV]

If you're going with Alumin(i)um, you need to avoid the 6xxx series alloys as they crack if you bend them (typically in the US, 6061 is most common, and in the UK it used to be 6082). You'll probably want a 5xxx alloy - the common one used to be 5083-O (-O means "annealed"). 5xxx are good for bending but horrible to machine, and 6xxx are the other way round (other classes of Al alloy are available)

If this is for a bike and might be exposed to the elements, watch out for potential intermetallic corrosion. I'd avoid putting alumin(i)um next to something copper-based like brass.

 

[Homeless Squirrel]

Myself i'd head to a "Decent"bike shop for some info/items as pretty sure they do step up/reducer rings for them?.
I know we had various items when was in the trade and others i knew that did more elaborate bikes/Frame building etc had even more.
But if your going down the make it yourself route? i'd head to somewhere that has a lathe be it model maker or machine shop and get a bit turned up either out of a higher grade of alloy like aircraft or Stainless steel or even a piece of frame tubing but only thing with steel is rusting!.
Myself i wouldn't bend a bit of alloy strip round it reason being is that area is under a lot of stress/force with impact back n forth of forks so really needs to be a ring so pressure is evenly spread out. esp with the rule of every action has an opposite!. Seen enough issues with forks and frames snapping!.

Post some pictures up of offending items so all can get a better idea.

 

[TRITON]

Any flat sheet, no matter what its thickness, has to suffer permanent deformation in order to form it into a circle.

I think theres a bit of a misunderstanding going on here.

Its not a flat sheet, its going to be a strip, approx 11mm wide, by say 150mm as its wrapping round the inset part of the cup, at a diameter of 49mm

After a bit of googling, it appears alloy, at a 1/2mm thickness, has a minimum bending radius of 6.35mm, and im looking to wrap it around a radius of about 24.5mm. So far as I can see alloy of that thickness is going to bend easily, in fact its not really bent, more curved than anything.

If this is for a bike and might be exposed to the elements, watch out for potential intermetallic corrosion. I'd avoid putting alumin(i)um next to something copper-based like brass.

Its alloy, going against alloy, with an anodized alloy against that. Corrosion isnt going to be an issue and tbh I been dealing with alloy bikes for years and they dont corrode that easily, and besides its basically hidden inside a tube with the end covered. And before hammering it home id smear the flange of the cup with grease. but in truth thats not really doing that much. I say this because basically the inside of a bike frame is bare metal, and doesnt corrode easily as ive yet to see one that has.

But if your going down the make it yourself route? i'd head to somewhere that has a lathe be it model maker or machine shop and get a bit turned up either out of a higher grade of alloy like aircraft or Stainless steel or even a piece of frame tubing but only thing with steel is rusting!.
Myself i wouldn't bend a bit of alloy strip round it reason being is that area is under a lot of stress/force with impact back n forth of forks so really needs to be a ring so pressure is evenly spread out. esp with the rule of every action has an opposite!. Seen enough issues with forks and frames snapping!.

Shimming is normal in the bike renovation game. I've shimmed many a seatpost, usually with alloy from a tin can, but this is a bit more than normal.

As to forces and stresses, theres little to none. A headtube is supported in two places, top/bottom and in all honesty theres no room for play when its all put in place. Plus this is a commuter type bike and is for pottering along. Im replacing a damaged alloy rigid fork with a basic(very very basic ) suss fork. (RST Volant 50mm travel)

This is the Ebike that im working on.
Pretty much zero stress going on it


This is my other Ebike
More stress going on this one lol

As you can see between the two, the city affair fork/headset rebuild is not going to experience anything that will cause me issues

 

[Jake]

I think it is too thin and flimsy, but that aluminium tape for foil faced insulation joints sprang to mind when someone mentioned tape above.

 

[Jameshow]

Have you tried a cycle bearing supplier like airevelo bearings* off eBay. They should be able to get you the correct bearing?
Other bearing suppliers are available.

 

[TRITON]

Have you tried a cycle bearing supplier like airevelo bearings* off eBay. They should be able to get you the correct bearing?
Other bearing suppliers are available.

Honestly James, its much better this way. I've thought it all out and the only way to get this done is to shim it. The bearings arent part of the equation.

 

[Jameshow]

Sure I had a mate sell a boardman frame because he couldn't find the right sized bearings...

 

[joshvegas]

This wouldn't have happened if you had kept your dyna-ti

 

[TRITON]

Ordered sheet - 200x150(I actually need 10x150mm, so ive bit spare

Cut it with scissors after scribing a line, it curled around the lower cup insert without puckering or folding and it tapped home fantastically. Seems all my measurements were spot on. not horribly tight, where you're worried it might split the headtube, and not slack where theres a risk of it turning as you turn causing wear and damage to the inside of the headtube.

Just front brake to fit/sort, + pedals and we're ready to go

Thanks for all the advice